DETERMINATION OF THE MAXIMUM DIAMETER FOR REINFORCED CONCRETE STRUCTURES

Reinforced concrete is the construction material widely used in the civil engineering field in the XX century; its excellent resistance characteristics and the material flexibility, that allowed plastic shapes due to formworks geometry that release the building plans from masonry walls, determine the material success. The growing knowledge about the material shows its high resistance and for this reason the construction workers have neglected to respect technological rules for the materials choice, packing and siting. The evaluation of a proper execution is entrusted exclusively to mechanical resistance tests, missing the aspects connected with a correct execution that determinate in this way the early decay of the material. The modern approach to the concrete structure (N.T.C. 2018) in the design poses as an essential requirement the material durability, through the determination of the Exposure Class, depending on aggressive environmental agents to which the structure is exposed; restoring in this way the importance of technological aspects and the relevance of the concrete design. Porosity is a very important property of the material and it can influence the useful life of the structures. It is the percentage in volume of voids compared to concrete total volume, so the aggressive agents penetrate more easily if porosity increases, attacking steel bars that are the most vulnerable members, because of their natural tendency to the oxidation. Therefore, the determination of aggregates mixture and the definition of the Maximum Diameter become a design essential phase, either for the reduction of internal and external wall effect, either for the total cover of the rebars. The determination of the concrete Maximum Diameter is assigned to three main parameters: concrete cover, spacing of bars, median radius of the formwork. The contribution submitted, that is a summary of a current research, highlights how parameters which are calculated in the design phase are incorrect in execution phase because of several interferences that in overlap areas and in the structural nodes occur, defining a potential crisis of the structure and technological inefficiency.